he nominated former senator chuck hagel for secretary of defense. hagel, a man who volunteered for vietnam, who was awarded two purple hearts for his courage. but tonight, he is already facing political fire. why? abc's chief global affairs correspondent martha raddatz tells us. >> reporter: president obama made clear today just how important this nomination is for the country. >> my most solemn obligation is the security of the american people. >> reporter: through decades of war and peace, the job of defense secretary has had profound implications. >> if forces to be used, saddam hussein would be removed from power. >> reporter: chuck hagel knows the horrors of war first hand. at 21, a poor kid from nebraska, he volunteered to go to vietnam, fighting side-by-side with his 19-year-old brother, tom. he got two purple hearts. one, when shrapnel ripped open his chest and his brother dragged him to safety. another, a month later, when hagel, himself on fire from a land mine, rescued his brother. >> i was on the left side, where the major blast came up,